This invention relates to a catalyst support for use in combination with a phosphate-containing catalyst. More particularly, this invention relates to a catalyst support for use with a phosphate-containing catalyst in a reaction where phosphorus in the form of a phosphate is being withdrawn or leached from the catalyst, thereby reducing the catalyst's effectiveness.
Phosphates are frequently employed as catalysts in various reactions, particularly in combination with iron or calcium, and possibly alkali or alkaline earth metals for use as mild oxidative catalysts. However, over a long period of continued use, these catalysts tend to deactivate because the phosphorus is slowly leached from the catalyst. This is particularly a problem in a continuous reaction where reactants flow over or through a catalyst bed. Several solutions have been suggested for this problem, particularly, the addition of phosphates into the feed or increasing the molar proportion of phosphates in the catalyst. These solutions have proved to be somewhat ineffective in preventing the deactivation of the catalyst.
It has been found that by using a phosphate-doped catalyst support which is physically mixed with the phosphate catalyst, the problem of phosphate leaching is substantially reduced or eliminated. The particular catalyst supports employed in the present invention comprises a mixture of an inert material, such as silica, titania, or zirconia in combination with a phosphate, preferably phosphoric acid.